The college, which has a motto “Coelesti Luce Crescat – May she grow in heavenly light”, defended the guidance.

It said it sent the letter in response to parents’ inquiries about what their daughters should wear for “Project Week”, when they are allowed to wear casual attire for activities including windsurfing.

Some parents also asked for guidance on dress code for social events, a spokesman added.

They told the newspaper: “We have found that working in collaboration with our parents has helped to balance current fashion trends with what is appropriate, bearing in mind our girls’ ages range from 11 to 18.”